Circuit Design

  Frequency modulation (FM) is a technique in which the frequency of a transmitted waveform is varied according to the variations in the message wave. The FM is a very popular technique since they are widely used by the FM radio stations. The main reason behind using the FM modulations by the radio stations is…

  The simple pulse modulation technique called Pulse Amplitude Modulation (PAM) proved to be more power efficient than the PWM and consumes constant power for individual pulses like PPM. In PAM the amplitude of the individual pulses are varied according to the amplitude of the modulating signals. The PAM modulator and demodulator circuits simple compared…

  Heat sensor senses the heat present around the sensor. When temperature rises above the set value, it will indicate the presence with the help of glowing LED. This heat sensor circuit can be used in kitchen or inside your PC. If your kitchen appliances or PC are over heated, it may be possible that…

  The electronic circuits like amplifiers, modulators etc. have a particular range at which they can accept the input signals. Any signals which have amplitude higher than this particular rage can cause distortion in the output of the circuit or may even cause damage to the circuit components itself. Since most of the devices works…

Here is a simple Solar Night lamp that turns on automatically at sunset and stays on till morning. It uses 1 Watt High Bright White LEDs to illuminate a confined area. 6 Volt 150 mA Solar panel is used to charge the battery during day time. This mini solar panel cost around Rs.300. Its positive…

This circuit can indicate the ON / OFF status of AC Loads. Two high bright LEDs indicate the power ON and power OFF status of the load connected to the AC outlet. It is highly useful to avoid the wastage of electricity if devices like heater, electric iron, Soldering iron etc are switched on unnecessarily…

Most of the electronic devices work on a single positive power supply except few like op-amps, oscillators etc. Majority of the amplifiers circuits or amplifiers ICs are also works on positive power supply. Such kind of devices can operate only with input signals having only positive voltages. Devices like amplifiers, modulators, demodulators etc. are supposed to work with natural signals as input. Since the natural signals like sine wave, audio signals etc. has both positive and negative cycles they have to be modified in such a way the single supply electronic circuits can operate them. Clamping is the common technique that is applied on the input signals to modify them so that the circuits can process the entire signal without losing either positive or negative half. In this method the entire waveform is shifted to positive of negative voltage side hence making them single polarity varying voltage.  

 Here is a simple circuit to protect TV from high voltage spikes during lightning or a power surge in the cable. It can be incorporated in the Coaxial cable of TV Antenna or Set top box. It uses a GDT and Safety capacitor to provide protection from high voltage spikes. The same circuit can also…

Some Microcontroller based Laboratory instruments such as Digital balance, pH Meter etc have rechargeable battery inside. This inbuilt battery should be properly charged for the error free operation of these instruments. If the instrument is not using (or charging) for long time, its inbuilt battery will be destroyed permanently. This charger timer circuit helps to keep…

The conventional mechanical energy meter is based on the phenomenon of “Magnetic Induction”. It has a rotating aluminium Wheel called Ferriwheel and [[wysiwyg_imageupload::]]many toothed wheels. Based on the flow of current, the Ferriwheel rotates which makes rotation of other wheels. This will be converted into corresponding measurements in the display section. Since many mechanical parts are involved, mechanical defects and breakdown are common. More over chances of manipulation and current theft will be higher.Electronic Energy Meter is based on Digital Micro Technology (DMT) and uses no moving parts. So the EEM is known as “Static Energy Meter” In EEM the accurate functioning is controlled by a specially designed IC called ASIC (Application Specified Integrated Circuit). ASIC is constructed only for specific applications using Embedded System Technology. Similar ASIC are now used in Washing Machines, Air Conditioners, Automobiles, Digital Camera etc. 

In this keypad lock project I have used the AT89S52 microcontroller, one of the series of 8051 microcontroller by ATMEL corp. Here I’m using 4X4 keypad to take input from the user (to enter password) and display the corresponding results on a 16X2 LCD. Since AT89S52 doesn’t have its own internal oscillator, thus we need to provide an external crystal of 11.0592 Mhz to make it function able. I am using a 7805 voltage regulator IC to convert 9V to desired 5V output.

‘Flex Sensor’ or ‘Bend Sensor’ is a sensor that changes its resistance depending on the amount of bend on the sensor. They convert the change in bend into electrical resistance – the more the bend, the more the resistance value.Flex sensors are widely used in various applications such as – Automotive controls, Medical Devices, Fitness Products, Virtual Reality gaming consoles, Animatronics, Robotics, etc.This tutorial aims to provide a detailed guide to flex sensor and its interfacing with Arduino. 

This simple circuit will act as a warning alarm whenever the temperature of a device exceeds above the safety level.  This circuit can be used to monitor the heat built inside the devices like your PC, inverters, CD player etc. As excessive heat may affect the sensitive component and may lead to permanent damage. The main advantage of this circuit is its compactness that’s why it can be easily install in the device itself. This circuit will also give you power on indicator of a device with the help of blinking LED. Therefore it attract your attention that device is on. This circuit uses a negative temperature coefficient (NTC) as a sensor to sense the heat. This circuit can be operated on wide range of temperature vary from 5V to 12V. 

Now a day’s everyone needs a device which could control appliances wirelessly. This makes us to operate them on our fingertips from particular vicinity with ease.This time I have done something like this, I have created a prototype of a device which controls 4 devices/appliances separately using RF (Radio Frequency) technology. The device comprises of two sections: Transmitting (remote) and Receiving part. The transmitting part works as a remote device to send the corresponding data to the receiver section. It further consists of 4 SPDT (single pole double throw) switch, one Encoder IC (HT12E) and a TX module (433 MHz). These 4 switches are connected to the 4 data pins of the encoder IC to generate a 4-bit data to be transmitted. The switches provide either high (+5V) or low (0V) signal levels. 

This power saving circuit is used to save electricity while ironing. The circuit will switch OFF the iron box when it is not in use. Once the ON time of the circuit is crossed, it will produce an alarm. If we press the Reset button at the time of alarm it will turned OFF the alarm and extend the ON time of the circuit to the next 4 minutes. This circuit will work as a reminder for those who always forget to turn OFF the iron box in this day to day busy life.In this circuit is build around NE 555(IC1), op-amp LM 358 (IC2) and few components. IC1 is designed as a standard monostable multivibrator and its trigger pin 2 is held high by resistor R1.LM 358 is configured as a comparator. Its non-inverting input (pin 3) and the inverting input (pin 2). Inverting pin 2 of IC2 is connected to voltage-divider preset VR1. Using preset VR1 we can vary the reference voltage at pin 2. Buzzer is connected to the output pin 1. Initially output pin 1 of IC2 is low.

Definitely, mosquitoes are annoying and it can spread diseases also. The best way to destroy mosquito is electronic killing using Swatter. It eliminates the use of toxic chemicals. The mosquito coils and liquids do not kill mosquito but they repel them only. Mosquitoes will return back when the chemical disappears from the atmosphere. The swatter is…

In industries, intruder alarms plays vital role in security. Existing industrial intruder alarms are wire based and alarms are placed on the wall. In this system a big alarm with loud sound works as alert. If some intruder enters then alarm activates and produces loud siren. Now consider another system. What if alarm is in hand of the security guards? There is only one sensor but there are several hand held simple alert alarms one with each security guard. Then it will become advance and impressive security system. But this is not possible with existing wire based system. To achieve this we have to transmit one signal to several alarms at a time and for that we have to use RF wireless technology. The new thing in this project is, it uses only one intruder sensing system and activates lot of hand held alarms. Means only one transmitter activates several receivers at a time. 

This is the most amazing and commercially viable project in which the web-cam attached to your computer will move in all four direction up-down and left-right with the help of your fingertips. The software written in VC++ will control two different AC motors with the help of computer mouse. The forward and reverse motion of…

The circuit presented here is used to transmit and receive low frequency pulses using IR modulator and demodulator. IR modulator takes low frequency pulses as input. It modulates them on 38 KHz carrier and transmits them through IR LED as 38 KHz IR light. On the demodulator side IR sensor detects (receives) 38 KHz IR light. It demodulates this 38 KHz pulses and recovers transmitted low frequency pulses. One pulse generator is built using IC555 to generate low frequency pulses. IR modulator is also built using IC555 and TSOP1738 IR sensor is used as IR demodulator. 

There are 2 cut off frequencies for band reject filter. First is the upper cut off frequency (f1) -which is the frequency below which all the frequencies are passed. The second is the lower cut off frequency (f2) – which are all the frequencies above this frequency are passed.Similar to band pass filter but the difference is f1 < f2. That means upper cut off frequency is lesser than lower cut off frequency. Two types of band reject filters are